London's first new purpose-built theatre since the Unicorn - and the first "West End" venue since the New London - has opened on the redeveloped site of the old Westminster Theatre at Victoria (just behind Billy Elliot) with a strong two-hander by Sandi Toksvig that should definitely put the place on the map.

Although first sampling suggests that the comfortable red square seats in the stylish 312-seater raked auditorium don't leave enough leg room, the overall impression is excellent: it "feels" fun, with a snazzy bar area, good toilets, and a wonderful marble staircase leading to an attractive-looking, light-filled brasserie.

Artistic director David Gilmore's first season looks low-key on paper, but Bully Boy, which has already been seen in Southampton and Northampton, is a pleasant surprise for a play that deals with combat stress in the Iraq war and is limited to a jostling, though progressive, relationship between a pukka wheelchair-bound major (Anthony Andrews at his glazed-eyed, fearsome best) and a Burnley squaddie (blazingly good newcomer Joshua Miles).

Oliver Hadley, the major, is a Falklands veteran leading the enquiry into his unit’s alleged involvement in the death of an eight-year-old local boy; Private Eddie Clark is the last of the soldiers to be interviewed, and is bristling with pent-up anxieties and aggression.

Patrick Sandford’s Nuffield Theatre production skilfully folds into this encounter other scenes of expedition and re-cap, including the key incident of a fatal explosion on the road, a plane trip back to England with empty coffins draped in Union Jacks, and a development, unlikely as it may seem, of the guarded friendship between the divorced officer and the 20-year-old skinhead.

The St James rises to simple technical challenges with aplomb (it remains to be seen how “epic” they can go on a small thrust stage); Simon Higlett’s design is a discreet mix of neutral screens and clever projections, while James Whiteside’s lighting and John Leonard’s sound are realised with high quality efficiency.

Andrews’ mask-like face of authority yields to the consequences of Eddie’s breakdown and, although the outcome remains uncertain to the end, there is enough flesh on the drama – including a lovely scene at the top of Pendle Hill in Eddie’s back yard – to negate a faint feeling of schematic contrivance to make a humanitarian point.

It is an astonishing fact, included in the play, that more Falklands veterans have committed suicide than were lost in the campaign itself. And like Owen SheersThe 2 Worlds of Charlie F, using the real-life stories of seriously injured Afghanistan veterans, the play vividly illustrates the difficulty of adjustment between the world you come from and the world you try to change in the name of your own freedom… if that is indeed the point of it all.